Development of Measurement Instruments for Space-Time Density Distribution of Floating Small Particles

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For the purpose of developing measurement instruments for the size and density of floating small particles, the present study investigates the following three methods.[1] Measurement method of small particles using a laser-beam scanning method The method is to derive the particle density and the particle-size spectra from the amplitude histogram of time-dependent random pulse signals obtained by detecting the light scattering from the small particles passing through the laser beam under illumination. Actual studies were performed in the following items: (1) optimum designs of the laser-beam scanning optical system and the detecting system, and their construction and improvement, (2) display method for the spatial distribution of time-integrated intensity of the scattering light, and analysis of the particle size and density, and (3) evaluation of passibly measuring particles and overall evaluation of the instrument. On the basis of these results, a measurement instrument was actually c … More onstructed.[2] Optical measurement method of small particles using moving transmission gratings The method, which is called spatial filtering velocimetry, is to detect, by means of a photodetector, the optical images of moving small particles through a transmission grating and to determine the velocity, size and density of particles by analyzing the frequency distribution of electric signals. Actual studies were conducted in the following items: (1) principle and theory of the methods, (2) measurements of the two-dimensional velocity using two rotating transmission gratings, (3) application of an image fiber to spatial filtering velocimetry, and (4) measurements of the particle density and size in spatial filtering velocimetry. On the basis of these results, several velocimeters were developed and constructed.[3] Measurement method of fine particle size using a speckle correlation technique The method is based on double-exposure speckle photography and is to measure the degree of correlation between the two speckle patterns produced from the same surface of a powder bed under two different laser illuminations. A preliminary study was performed to verify the usefulness of the method and to show the possibility of its use in an on-line measuring process. Less